1. Field of the Invention
The present invention relates generally to a method and apparatus for connecting two or more fluid carrying tubes. The method and apparatus of the present invention have particular utility for connecting blood carrying medical tubing in a continuous fluid circuit without introducing bubbles or other environmental contaminants into the tubing, but may be used for connecting any two or more fluid carrying tubes.
2. Description of the Prior Art
Extracorporeal procedures are well known. In these procedures, blood generally is withdrawn from a patient through cannulation, treated (e.g. by pumping, oxygenation, filtering, or the like), and reintroduced to the patient through cannulation. For example, in a cardio-pulmonary bypass procedure, blood may be withdrawn through cannulation at a first site upstream of an occlusion site, pumped, and reintroduced through cannulation at a second site downstream of the occlusion site.
Each of these extracorporeal procedures requires a stage of connecting one blood carrying tube, such as a cannula, to another blood carrying tube, or to another element, such as an external pump, to provide a continuous fluid circuit. This stage of the procedure requires great care in preventing introduction of air or other contaminants into the fluid circuit. In particular, air bubbles can cause embolism or other medical complications that may be harmful or fatal to the patient.
For example, in one conventional procedure, each of a cannula and a tube typically are primed with a conventional priming fluid, such as a saline-based priming solution, and then clamped at a location proximate the end portion thereof, to assure that each is filled as full as possible with such fluid. The open ends of the primed cannula and blood tube then are connected slowly under a continuous stream of solution, e.g., from an external syringe, to provide a bubble-free fluid connection. A variation of this technique may be used when the fluid circuit includes a roller-type pump. In this variation, a perfusionist rotates the pump head of the pump in a forward direction to perform a "roll-up" technique, which continuously advances priming fluid out of the blood tube during the connecting stage.
These techniques have a number of drawbacks. First, each technique requires a degree of training to make a bubble free connection. For example, in the former technique, connection under a stream of fluid may cause air entrainment, resulting in bubbles in the tubing. The latter technique is well suited to a roller-type pump, and may not be easily adapted for use with a centrifugal pump, or the like. Each of these techniques requires two people to perform the connection. Also, after completion of the connection, it often is not possible to disassemble the cannula and tubes if bubbles then are detected in the tubes. Moreover, since these techniques are not easily repeatable, they are not desirable in the case of an emergency procedure.
It is also known in the art to use a connector tube for connecting two-fluid carrying tubes at respective open ends thereof. Such a connector tube preferably is a short, rigid cylindrical tube, and may include securing structure, such as barbs, at each end thereof for rigidly and securely connecting the previously open ends of the fluid carrying tubes to form a continuous fluid channel or circuit.
An improvement on this technique includes a hard, barbed, connector tube provided with a branch or side-arm luer port. The luer port may be used for collecting and eliminating any air bubbles trapped in the fluid circuit after connection.
These techniques also have a number of drawbacks. Initially, when a connector tube is inserted in the open end of one fluid carrying tube, it functions as an extension of that tube for connecting to the second tube. Thus, this system includes all of the above-discussed drawbacks. The branches or luer fittings also have a drawback in that they introduce an element that protrudes from the fluid circuit during procedure. This protrusion may catch on surrounding objects or accidentally be broken off, resulting in inconvenience or possibly major blood loss during procedure. Moreover, these protrusions form vestiges that remain on the side wall of the connector tube of the fluid circuit. These vestiges are discontinuities that form stagnation zones in the fluid circuit that tend to cause thrombus. Thrombus can cause other medical complications that may be fatal to the patient.